The present invention relates to a pattern forming apparatus and a pattern forming method where a magnetic field is applied to a coating composition which contains magnetic particles with flaky form during and after application of the coating composition to, for example, an article to be coated which is a nonmagnetic particle, and thus, the magnetic particles are oriented, so that a pattern is formed through orientation of the magnetic particles.
Conventional methods have been proposed for forming a pattern on a coating film where a coating composition containing magnetic particles is applied to the surface of an article to be coated and thereafter the magnetic particles are oriented by a magnetic field that is created by a magnet so that letters or figures emerge. Japanese Laid-Open Patent Publication No. 5-337424 discloses an apparatus for manufacturing a molded article having a coating film where a pattern is formed as described above. This manufacturing apparatus is provided with a supporting means for supporting the main body of a molded article, a coating film forming means for forming a coating film by applying a transparent or translucent coating composition in liquid form in which magnetic particles with flaky form are mixed on the surface of the main body of the molded article, magnetic field forming means for applying a magnetic field to the magnetic particles in the coating film and a magnetic field changing means for changing the magnetic field. In the magnetic field forming means, a first magnet and a neighboring second magnet are placed at a distance from each other so that a magnetic field (lines of magnetic force) is created so as to extend from the N pole of the first magnet to the S pole of the second magnet.
The magnetic particles which are mixed in with the coating composition easily settle and aggregate during storage, and furthermore, easily settle in the application machine at the time of application, and therefore, in some cases, distinctness in the border portions in the formed pattern and appearance of depth in the pattern cannot be produced. Therefore, it has been proposed that particles where magnetic particles are coated with a synthetic resin or mica coated with a magnetic material be used, in order to achieve reduction in weight for the magnetic particles. In this case, the specific weight of the magnetic particles is small, making it difficult for the magnetic particles to settle and aggregate, and thus, a uniform pattern can be produced, in comparison with the above described prior art. The synthetic resin and the mica are nonmagnetic particles, however, and therefore, the magnetic particles are not oriented as intended under some conditions at the time of application, and thus, a satisfactory appearance cannot be achieved. In order to solve this problem, a magnetic pattern forming coating composition has been proposed where the coating composition is set so that the solid component in the coating film one minute after application becomes 70 weight % or less as described in Japanese Laid-Open Patent Publication No. 2003-176452.
In the magnetic field forming means of the manufacturing apparatus described in Japanese Laid-Open Patent Publication No. 5-337424, however, the direction of the lines of magnetic force in the magnetic field is set approximately parallel to the surface of the coating film approximately in the center portion of the outline of a pattern, that is to say, approximately in the center portion between the end of the first magnet and the end of the second magnet. In other words, the extreme value (maximum value) of the lines of magnetic force directed from the N pole to the S pole is located approximately in the center portion between the end of the first magnet and the end of the second magnet. Therefore, the portion of the pattern created through orientation of magnetic particles in a magnetic field has a great width, making the pattern faint, and thus, distinctness cannot be achieved in the pattern. Furthermore, the magnetic particles located deep in the coating film are also oriented in the manner described above, and thus, a problem arises, such that appearance of depth cannot be achieved in the pattern and the appearance of movement resulting from shifting of the pattern when viewed from different angles is not satisfactory.
In the pattern forming coating composition described in Japanese Laid-Open Patent Publication No. 2003-176452, the coating composition is set so that the solid content of the coating composition one minute after application becomes only 70 weight % or less. Therefore, even when a magnetic field is applied and the magnetic particles in the coating composition are oriented in the direction of the lines of magnetic force, the viscosity of the coating composition does not subsequently increase sufficiently and the orientation of the magnetic particles is not maintained. Accordingly, a problem arises, that distinctness, depth appearance, and appearance of movement cannot be improved in the pattern due to disturbances during orientation of the magnetic particles.